Rusted strip for the bellypan is weak at points.Replace with 14g steel and rivet to outriggers?
How should I address the damage by the door?Can I treat with POR and scab a new piece over(or under) the damage?

Hey Steve, That doesn't look so bad on the step pic. Is it possible to weld a piece under the one with the windows in it? If it can be done underneath it won't have to be a bump in your floor later on. You can POR-15 after and it will be great.
The strip under the bellypan didn't exist on my safari. Did you notice if this was opened up prior to your work on it? Maybe it's a repair. If it's steel it most certainly was a repair, as airstream only used aluminum on the pans I've seen. If you need it there you should replace it with a piece of aluminum of a fairly heavy gage (about 1/16") and it will last through several more owners. Also, get the wide-flange rivets for re-assembly of the pan if you haven't already. They are hard to pull with a manual rivet gun but they will outlast the pan material.
Your frame rust looks very much like mine did with the exception of the holes. I had one hole where a welder blew a 3/4" hole in an intersection of a crossmember and a center strap. That was a surprise.
I also had a few areas where the original black paint looked like it was just sprayed yesterday, and I couldn't get it off with a wire cup on a drill.

This is the first picture I took after beginning to pull up the floor. I recall trying not to gag when I took it. You could blow it up full-screen and play Where's Wally with it, see if you can find any animals The second one is just after removing all of that and cleaning the pan. Then there's the racing frame, just before putting the new floor back down. I hated to cover it back up after all of that work!
I like to look back now and then at these to remind myself how much I've done.

Hey Steve, That doesn't look so bad on the step pic. Is it possible to weld a piece under the one with the windows in it? If it can be done underneath it won't have to be a bump in your floor later on. You can POR-15 after and it will be great.
The strip under the bellypan didn't exist on my safari. Did you notice if this was opened up prior to your work on it? Maybe it's a repair. If it's steel it most certainly was a repair, as airstream only used aluminum on the pans I've seen. If you need it there you should replace it with a piece of aluminum of a fairly heavy gage (about 1/16") and it will last through several more owners. Also, get the wide-flange rivets for re-assembly of the pan if you haven't already. They are hard to pull with a manual rivet gun but they will outlast the pan material.
Your frame rust looks very much like mine did with the exception of the holes. I had one hole where a welder blew a 3/4" hole in an intersection of a crossmember and a center strap. That was a surprise.
I also had a few areas where the original black paint looked like it was just sprayed yesterday, and I couldn't get it off with a wire cup on a drill.

This is the first picture I took after beginning to pull up the floor. I recall trying not to gag when I took it. You could blow it up full-screen and play Where's Wally with it, see if you can find any animals The second one is just after removing all of that and cleaning the pan. Then there's the racing frame, just before putting the new floor back down. I hated to cover it back up after all of that work!
I like to look back now and then at these to remind myself how much I've done.

Best to you Steve

Rich the Viking

Thanks Rich!I was thinking a scab piece would work under.I think I have room.The strips ran along the sides tak welded to the outriggers.It looks factory to me.They are steel and the skirt and bellypan overlap there and are riveted to this piece.They were painted black at one time.I cut off flush with the outrigger so I will have to grind the weld and remainder of metal off.The aluminum idea is a good one because this strip was riveted right on the aluminum.
In your frame pic was this about where you started POR.I used a knot wire brush on my 7in.grinder and it took alot to bare metal .paint came right off with this.I have removed all the flaking stuff and wondering how much cleaner it needs to be.Here's a pic.Even cleaner now.
The weather has been 65-70 all week.This weekend SNOW! That's Texas.Now I know why my daughter lives in Santa Monica.

Thanks Rich!I was thinking a scab piece would work under.I think I have room.The strips ran along the sides tak welded to the outriggers.It looks factory to me.They are steel and the skirt and bellypan overlap there and are riveted to this piece.They were painted black at one time.I cut off flush with the outrigger so I will have to grind the weld and remainder of metal off.The aluminum idea is a good one because this strip was riveted right on the aluminum.
In your frame pic was this about where you started POR.I used a knot wire brush on my 7in.grinder and it took alot to bare metal .paint came right off with this.I have removed all the flaking stuff and wondering how much cleaner it needs to be.Here's a pic.Even cleaner now.
The weather has been 65-70 all week.This weekend SNOW! That's Texas.Now I know why my daughter lives in Santa Monica.

The new strips could just be riveted onto the outriggers before you put the pan back up.
I used a rust convertor on my frame(Jasco) and a rusted-metal primer and paint from rustoleum, instead of POR-15. I didn't try to get to bare metal, just to get rid of loose rust and paint. I hear that with POR-15 you dont need to be completely thorough in removing rust either. You may want to read up on that in the forum as I don't have personal experience with it. Maybe someone else will chime in here with that info.
We had 40 degrees at my house this morning, and ten miles up the road it was 59. Very strange!

With the Por-15 you use a wire brush & get off the loose rust. Then you wash it down with their product called "Marine Clean". This removes any grease that may be on the metal. After that, you spray it with their product called "Metal Ready". You keep it wet for 10-20 minutes. This etches the metal so the paint will adhere to any spots that may be really smooth (like areas under the floor where they were never exposed to any weather). THEN you apply the Por-15. Two coats are recommended & they have to be applied within 5 hours of one another or you have to sand it all again (never want to do that!) It's a series of steps, the end result is VERY hard coating. I love it & wore it for a week to prove it! (It can't be removed with paint thinner).

I have been working steady a couple of days a week since Jan.1 I chose to do frame on since I did not want to have shell off outside(wind).
It was really easy.Floor off,clean BP,remove BP,and work on frame standing on the ground.Tomorrow clean frame and metal etch.When the first low humidity day comes I will do POR.Great advice from Rich Viking on frame on and Ewe helped me find two suitable tanks at Ronco tanks for gray and black and even gave me a roadmap for install.
Ambie 64 suggested polishing up one spot to look at every day to help keep me moving forward.Stay focused and don't get too many things going at a time!

I work full time active duty military, full time student (five classes), and of course this Airstream...to late on the too many things. Well you take a deep breath and live in the moment and work till ya drop!

I'll hopefully finish prepping my frame this week, and POR it this weekend. The instructions on the can state "POR-15 is cured and strengthened by exposure to moisture and will dry faster under extreme humidity." You might want to reconsider that low humidity day.

I have been working steady a couple of days a week since Jan.1 I chose to do frame on since I did not want to have shell off outside(wind).
It was really easy.Floor off,clean BP,remove BP,and work on frame standing on the ground.Tomorrow clean frame and metal etch.When the first low humidity day comes I will do POR.Great advice from Rich Viking on frame on and Ewe helped me find two suitable tanks at Ronco tanks for gray and black and even gave me a roadmap for install.
Ambie 64 suggested polishing up one spot to look at every day to help keep me moving forward.Stay focused and don't get too many things going at a time!

quick question... i was under the impression that an advantage of doing a frame-on restoration is that you do not need to remove the belly pan (and therefore do not need to deal with the buck rivets around the waste-line). did you somehow remove the belly pan without messing with the buck rivets?

Drop only the center of the belly pan and leave the edges intact if you can. I didn't need to drill out any bucked rivets on mine but yours may be different. You'll need it down so you can get the floor bolts through the frame and tighten them from below.
Cheers!
Rich the Viking